Continuous feed nibbling apparatus

ABSTRACT

The workpiece positioning means for the punch press is provided with biasing means for allowing temporary relative movement between the workpiece holding means and the drive for moving the workpiece holding means while the punch is in the workpiece and for restoring the workpiece holding means to its original relative position with the drive after the punch is removed from the workpiece during a nibbling operation.

United States Patent [1 1 1111 ,839,936 Daniels [4 Oct. 8, 1974 CONTINUOUS FEED NIBBLING APPARATUS Inventor: Dennis Daniels, Bellevue, Wash.

US. Amada Ltd., Seattle, Wash.

Nov. 20, 1972 Assignee:

Filed:

Appl. No.:

11.8. C1 83/410, 83/413, 83/916 Int. Cl 826d 7/06 Field of Search 83/409, 409.1, 409.2, 410,

References Cited UNITED STATES PATENTS 12/1952 Johnson et a1. 83/269 X H1966 Kihlstrom et a1. 83/413 X Primary Examiner-Andrew R. Juhasz Assistant Examiner-W. R. Briggs Attorney, Agent, or Firm-Seed, Berry, Vernon & Baynham 5 7 ABSTRACT The workpiece positioning means for the punch press is provided with biasing means for allowing temporary relative movement between the workpiece holding means and the drive for moving the workpiece holding means while the punch is in the workpiece and for restoring the workpiece holding means to its original relative position with the drive after the punch is removed from the workpiece during a nibbling operation.

13 Claims, 6 Drawing lFigures CONTINUOUS FEED NIBBLING APPARATUS BACKGROUND OF THE INVENTION I. Field of the Invention This invention pertains to punch presses and more particularly to workpiece feeding apparatus for such punch presses.

2. Description of the Prior Art A nibbling operation is done with a punch rapidly reciprocating into and out of a workpiece with the workpiece being moved either manually against the punch or by a numerically controlled workpiece positioning mechanism. The movement of the workpiece positioning mechanism is relatively slow, in some cases less than one-half the potential speed of reciprocation of the punch, due to the fact that the workpiece moving mechanism must wait until the punch is out of the workpiece before it again begins to move the workpiece. In the eccentric drive type of punch press, for example, the punch can be in the workpiece for as much as one-quarter of a revolution of the eccentric or onequarter of a complete reciprocating stroke of the punch.

In prior art machines, a signal is normally sent to the workpiece moving mechanism to indicate that the punch has become completely free from the workpiece; next the workpiece is fed to its new position, and a second signal is sent to the punch drive when the workpiece reaches its new position; next the punch again begins its downward travel and the workpiece positioning means stops movement as the punch enters the material. The stopping and starting of the workpiece positioning means and the punch drive, both of which constitute considerable mass, slows considerably the potential nibbling speed at which the punch can operate.

SUMMARY OF THE INVENTION It is an object of this invention to provide a workpiece feeding apparatus that allows the punch to reciprocate continuously in the nibbling mode.

It is another object of this invention to provide a workpiece positioning means that allows the drive for the workpiece positioning means to operate continuously during a nibbling operation.

Still another object of this invention is to provide adjustable resilient means for restoring the relative position between the workpiece hodlding means and the drive for moving the workpiece holding means.

These objects are best obtained by providing means for rapidly reciprocating a punch in a nibbling mode, means for positioning the workpiece relative to the punch, said workpiece positioning means including means for holding the workpiece and drive means for moving the workpiece holding means, and means for allowing both the punch reciprocating means and the drive means to operate continuously throughout the nibbling operation.

In the preferred form, the connection between the workpiece holding means and the drive means for moving the holding means, includes a resilient or resilient lost-motion mechanism that allows the holding means to stop during the engagement of the workpiece by the punch but upon withdrawal of the punch from the material the resilent means rapidly overtakes the drive means to reposition the workpiece prior to the next stroke of the punch. In one form. of the invention the resilient means includes springs and in another form of the invention the biasing means includes adjustable springs such as a pressurized air supply. In one embodiment of the invention, the air supply is responsive to a sensor indicating the position of the punch relative to the workpiece so that the air pressure and thus the biasing force can be varied depending upon whether the punch is in or out of the workpiece.

The advantages of this invention are readily apparent. Assuming, for example, a potential nibbling speed of reciprocation of the punch at 200 hits or strokes per minute and a workpiece positioning speed of inches per minute, the full potential of the 200 hits per minute stroke can be realized since the mass attached to the punch and the mass associated with the workpiece positioning mechanism need not be stopped and started with each stroke of the punch. The potential speed, in fact, at which the punch can reciprocate, is dependent almost entirely upon the speed with which the resilient lost-motion biasing mechanism can restore the workpiece to the position at which it would have been, had not the workpiece been engaged by the punch. This recovery speed is extremely fast for springs and other air spring type biasing mechanisms and potentially can be faster than the speed of any known punch reciprocating mechanism.

With an adjustable spring, different sizes and weights of workpieces can be accommodated and with punch sensors detecting when the punch is in and out of the workpiece it is possible to change the air pressure to increase the speed with which the workpiece recovers its desired position.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS FIG. 1 is a plan view of a workpiece positioning mechanism embodying the principles of the invention.

FIG. 2 is a fragmentary vertical section taken along 2-2 of FIG. 1.

FIG. 3 is a fragmentary section taken along the lines 3-3 of FIG. 2.

FIG. 4 is a view similar to FIG. 3 illustrating a preferred modification of a device shown in FIG. 1 and employing an air spring configuration.

FIG. 5 is a fragmentary vertical section taken along the line 5-5 of FIG. 4.

FIG. 6 is a vertical fragmentary section illustrating still another modified embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As best shown in FIG. 1, workpiece positioning means 12 are clamped to a workpiece W which is supported on a work table or surface 14. The workpiece positioning means and table are a part of a punch press preferably of the type illustrated in US. Pat. No. 3,717,061 the description of which is incorporated herein by reference thereto. As is well known with punch presses, the workpiece positioning means locates the workpiece beneath a punch in both the X and Y axes of movement simultaneously or independently preferably by a numerical control. Typically, the feed rate of the workpiece is one thousand inches per minute during standard punching operations in which the punch is removed from the material and the workpiece moved a considerable distance to the next punching location. A typical eccentrically driven punch operates at 90 revolutions per minute in this standard punching mode. Most punch presses have an additional operating capability known as nibbling. In nibbling, the reciprocatory speed of the punch is increased typically to about 200 strokes per minute and the feed rate of the workpiece is reduced to a much smaller speed, typically 100 inches per minute. Typically, during nibbling operations, the punch is within the workpiece roughly 25% of the revolution of the eccentric or 25% of each down and up stroke of the nibbling punch. The nibbling punch can take many forms one of which would be a square punch taking, for example, a one-half inch cut with each stroke at the above speeds and is typically used to form slots such as the one indicated by the reference numeral 15. The numerical control of the workpiece positioning means, however, also allows a round punch to be used to cut an irregular slot such as that indicated by the reference numeral 16. In this invention, the punch and the workpiece positioning drive can be run continuously during nibbling for either of the operations suitable for cutting the slot or 16 or for any other nibbling operation.

The workpiece positioning means includes a moving means or drive 18 having a conventional worm gear 20 that drives a carriage 22. Lost-motion-biasing means are provided between the drive means and the workpiece gripping clamps 24 to allow the workpiece to stop movement as the worm gear 20 continues to drive the transport or carriage 22 during the period the punch is within the workpiece and at the moment the punch leaves the workpiece, moves the clamps to catch-up to the original relative position of the clamps with the carriage 22.

In the preferred embodiment, the lost-motion-biasing means includes a housing 26 that is adjustably secured to the carriage 22 by conventional jaws 28. The housing is joined to the clamps 24 by a transfer plate 30 that is secured to the clamp 24 and to a floating plate 32 forming part of the housing. The floating plate 32 can be rigidly secured in the housing 26 by a pneumatically actuated shot-pin 34 which upon receipt of pressure from an air line 36 drives the shot-pin into a conical opening, 38. In this position, the workpiece clamp and the housing 26 are rigidly locked together for normal or conventional positioning of the workpiece either in the punching mode or for transporting the workpiece to different locations to begin successive nibbling modes.

As best shown in FIG. 3, one embodiment for providing a biased self-centering, lost-motion, interconnection between the floating plate 32 and the housing 26 is provided by a plurality of springs 40 each housed in a hollow centering post 42 which is slidably received in a horizontal bore 44. The outer end of each bore is capped by an adjustableplug 46 to serve as a stop against outward movement of the spring. The inner end of the post 42 is provided with a shoulder 48 that engages against the inner end of the bore 44 to limit inward movement of the post 42. As shown in FIG. 3, the four posts when positioned in their innermost condition center the floating plate 32 within a circular recess 50 provided in the housing 26. In a preferred form assuming a nibbling speed for reciprocating the punch at 200 hits per minute and a workpiece feeding speed of 100 inches per minute a cutting bite by the punch equals one-half inch per hit, and assuming the punch is in the material for approximately 25% of its reciprocable stroke, it can be seen that the gap x between the centered position of the plate 32 and the outer diameter of the recess must be at least one-eighth of an inch. This one-eighth of an inch represents the floating ca pacity of the plate so that the carriage 22 can continue to move while the workpiece is held stationary. As another example assuming 200 hits per minute and a feed rate of 200 inches per minute, it can be seen that each cut of the punch will be one inch per hit. Assuming again that the punch is in the material for 25% of its up and down stroke, it can be seen that the size of the recess 50 must provide for a one-quarter inch float capacity.

As is well known in this art, the clamps 24 are closed by pneumatic pressure acting on a piston 54 via a line 55. The introduction of air pressure to the top of the piston 54 pushes the top clamp 56 about a pivot 58, counter-clockwise as shown in FIG. 2, and against a release spring 60. Termination of the air pressure through line allows the spring 60 to rock the clamp 56 clockwise to open the clamp for insertion or removal of the workpiece.

In some instances, the weight of the workpiece W will cause sufficient frictional drag as it is moved across the table 14 to skew the clamps about the axes of the floating plates. Several techniques may be provided to prevent this. In the preferred embodiment, a bar 62 joins both sets of clamps 24. The bar is releasably secured to the clamps by set screws 66. When the bar 62 is locking the two clamps together, neither can skew relative to the axis of the floating plates and thus move in parallelism. The set screws 66 and the jaws 28 are, of course, both releasable so that the workpiece clamps 24 can be moved relative to one another to accommodate various sized workpieces.

A second embodiment of the invention is illustrated in FIGS. 4 and 5. In this embodiment, the floating plate 32 is again centered in the circular recess 50 in the housing 26. Rather than using mechanical springs, however, this embodiment employs adjustable springs in the form of a plurality of pistons 68 attached to centering posts 70. The pistons slide in bores 72 and the inner ends of the pistons abut against the inner ends of the bores 72 to limit the inward movement of the centering posts 70. Air at a predetermined pressure is applied through a common channel 74 and biases each of the pistons toward the center of the plate 32 thus centering the plate in the recess 50. The plate can be moved, however, in any direction provided it has received sufficient force to compress the air behind the piston in the direction to which it is urged. Air behind the piston or pistons being pushed by the floating plate 32 will compress in channel 74 and upon release of the pressure acting on floating plate 32, will restore the pistons to their innermost positions again centering the floating plate. The air pressure can be a constant for any particular workpiece, the amount of pressure being dependent upon the weight of the workpiece and the amount of friction necessary to overcome when centering the floating plates. Preferably, however, the desired air pressure would be minimized while the punch is in the workpiece and thus the workpiece is being held stationary and maximized when the punch leaves the workpiece and the floating plates are being urged back into their centermost positions as in the next-described embodiment.

Another embodiment of this invention is to synchronize the position of the punch relative to the workpiece with the amount of pressure being applied on the pistons acting against the floating plate 32. As stated above, this provides the optimum responsiveness in restoring the workpiece to its original position. To accomplish this function, a schematic illustration is shown in FIG. 4 which includes a pressurized air line 80 connected to the pressurized air supply 82 by a two way valve 84. A sensor S, of a type well known in the art, determines when the punch P is in or out of the workpiece W. When the punch is in the workpiece, the sensor S sends a signal to the valve 84 to reduce the pres sure in line 80 to between about zero to psi. When the sensor determines the punch is out of the workpiece, it again sends a signal to valve 84 to immediately increase the pressure to about 100 psi so that the workpiece is restored quickly by the pistons to the same location it would have been if the workpiece had been rigidly coupled to the drive 18.

Still another embodiment of the invention is illustrated in FIG. 6. In this embodiment two shot-pins 90 are driven into conical bores 92 in the floating plate 32 to not only lock each floating plate 32 in its housing 26 but also align it about its center of rotation. In this embodiment, the workpiece clamps 24 and the workpiece W become a rigid linkage for maintaining squareness of the floating plates 32 about their axes of rotation. That is, if sufficient clamping force is provided on the workpiece, the two workpiece clamps 24 and the workpiece become a rigid link to prevent skewing of the clamps about their respective centers of the floating plates 32. The disadvantage of this embodiment is that the workpiece clamps must be designed to have sufficient strength and clamping force to effect the rigid connec tion with-the workpiece and, of course, the workpiece itself, must be of sufficient thickness to complete the rigid link.

While the preferred embodiments of the invention have been illustrated and described, it should be understood that variations will be apparent to one skilled in the art without departing from the principles of the invention. Accordingly, the invention is not to be limited to the specific embodiments described.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. Apparatus for providing continuous workpiece feeding in a nibbling operation of a punch press comprising means for supporting a sheet material workpiece to be punched,

punch means operable in a nibbling mode to rapidly reciprocate a punch through a workpiece, workpiece positioning means for moving the workpiece over the supporting means,

said workpiece positioning means including means for holding the workpiece, means for moving the workpiece holding means to advance the workpiece. and biasing means for allowing temporary relative movement between the holding means and the moving means while the punch is in the workpiece and for restoring the holding means to its original relative position with the moving means after the punch is removed from the workpiece.

2. The apparatus of claim 1 said biasing means including housing means coupled to said moving means, floating plate means resiliently coupled to said housing means and rigidly secured to said workpiece holding means, and means for resiliently holding said plate means centrally in said housing means.

3. The apparatus of claim 1 said biasing means including an adjustable air supply, and a plurality of airactuated pistons.

4. The apparatus of claim 2 said means for moving said workpiece holding means including a feed screw.

5. The apparatus of claim 1 said workpiece holding means including at least two workpiece engaging clamps and means for selectively locking said clamps together for conjoint movement to prevent skewing of the clamps relative to said moving means.

6. The apparatus of claim 1 said biasing means including latch means for preventing said temporary relative movement between the holding means and the moving means for use in regular punching operations.

7. The apparatus of claim 5 said biasing means including housing means coupled to said moving means. floating plate means resiliently coupled to said housing means and rigidly secured to said workpiece holding means, and means for resiliently holding said plate means centrally in said housing means.

8. The apparatus of claim 7 said means for resiliently holding said floating plate means centrally including a plurality of pistons equidistantly spaced around said floating plate means, means for providing pressurized air against said pistons for biasing said pistons centrally, said housing means including a recess for receiving the plate means and allowing limited lateral movement of the floating plate means in said recess, each said piston including a rod having an end engaging the floating plate means when the piston is bottomed out in said housing means so that the floating plate means can move only by overcoming the pressurized air.

9. The apparatus of claim 7 said. means for resiliently holding said floating plate means centrally including a plurality of hollow posts biased centrally by mechanical springs.

10. The apparatus of claim 3 said adjustable air supply including means for sensing the presence of the punch in and out of the workpiece and control means responsive to said sensing means for lowering the pressure acting on said pistons when the punch is in the workpiece and raising the pressure acting on the pistons when the punch is out of the workpiece.

11. The apparatus of claim 8 said means for providing pressurized air including means for raising and lowering the pressure of the air, a sensor for determining the location of the punch in and out of the workpiece, and air pressure control means responsive to said sensor for lowering the air pressure when the punch is in the workpiece and raising the air pressure when the punch is out of the workpiece.

l2. Nibbling apparatus for rapidly punching an opening in a workpiece comprising means for continuously reciprocating a punch into and out of the workpiece at a high rate of speed during a nibbling operation, means for positioning the workpiece in any direction in a horizontal plane beneath the punch and relative to a vertical axis through the center of the punch, said positioning means including workpiece holding means and drive means continuously operating during a nibbling operation for moving the workpiece holding means relative to said vertical axis, and means for providing a pause in the relative movement between said workpiece holding means and said vertical axis while the punch is engaged in the workpiece and for restoring the relative position between the workpiece holding means and the vertical axis to the relative position each would have had if there had been no pause in relative movement for allowing the punch reciprocating means and the drive means to be operated continuously as the workpiece is moved in any direction in said horizontal plane while being punched without permanently affecting the relative position between the workpiece holding means and the vertical axis during an entire nibbling operation.

13. Nibbling apparatus for rapidly punching an opening in an independent workpiece sheet comprising means for reciprocating a punch into and out of a sheet at a high rate of speed, means for positioning the sheet beneath the punch in the X and Y axes, said positioning means including sheet holding means and drive means for moving the sheet holding means in the X and Y axes, and sheet floating means for allowing the punch reciprocating means and the drive means to be operated continuously without bending the sheet as the sheet is being punched, said sheet floating means including means operable to move the sheet with the drive means while the punch is disengaged from the sheet, to allow the punch to stop the sheet when the punch is in the sheet by effecting relative movement between the holding means and the drive means, and to reposition the holding means relative to the drive means when the punch is removed from the sheet to return the sheet to a position which it would have had if not stopped by the punch. 

1. Apparatus for providing continuous workpiece feeding in a nibbling operation of a punch press comprising means for supporting a sheet material workpiece to be punched, punch means operable in a nibbling mode to rapidly reciprocate a punch through a workpiece, workpiece positioning means for moving the workpiece over the supporting means, said workpiece positioning means including means for holding the workpiece, means for moving the workpiece holding means to advance the workpiece, and biasing means for allowing temporary relative movement between the holding means and the moving means while the punch is in the workpiece and for restoring the holding means to its original relative position with the moving means after the punch is removed from the workpiece.
 2. The apparatus of claim 1 said biasing means including housing means coupled to said moving means, floating plate means resiliently coupled to said housing means and rigidly secured to said workpiece holding means, and means for resiliently holding said plate means centrally in said housing means.
 3. The apparatus of claim 1 said biasing means including an adjustable air supply, and a plurality of air-actuated pistons.
 4. The apparatus of claim 2 said means for moving said workpiece holding means including a feed screw.
 5. The apparatus of claim 1 said workpiece holding means including at least two workpiece engaging clamps and means for selectively locking said clamps together for conjoint movement to prevent skewing of the clamps relative to said moving means.
 6. The apparatus of claim 1 said biasing means including latch means for preventing said temporary relative movement between the holding means and the moving means for use in regular punching operations.
 7. The apparatus of claim 5 said biasing means including housing means coupled to said moving means, floating plate means resiliently coupled to said housing means and rigidly secured to said workpiece holding means, and means for resiliently holding said plate means centrally in said housing means.
 8. The apparatus of claim 7 said means for resiliently holding said floating plate means centrally including a plurality of pistons equidistantly spaced around said floating plate means, means for providing pressurized air against said pistons for biasing said pistons centrally, said housing means including a recess for receiving the plate means and allowing limited lateral movement of the floating plate means in said recess, each said piston including a rod having an end engaging the floating plate means when the piston is bottomed out in said housing means so that the floating plate means can move only by overcoming the pressurized air.
 9. The apparatus of claim 7 said means for resiliently holding said floating plate means centrally including a plurality of hollow posts biased centrally by mechanical springs.
 10. The apparatus of claim 3 said adjustable air supply including means for sensing the presence of the punch in and out of the workpiece and control means responsive to said sensing means for lowering the pressure acting on said pistons when the punch is in the workpiece and raising the pressure acting on the pistons when the punch is out of the workpiece.
 11. The apparatus of claim 8 said means for providing pressurized air including means for raising and lowering the pressure of the air, a sensor for determining the location of the punch in and out of the workpiece, and air pressure control means responsive to said sensor for lowering the air pressure when the punch is in the workpiece and raising the air pressure when the punch is out of the workpiece.
 12. Nibbling apparatus for rapidly punching an opening in a workpiece comprising means for continuously reciprocating a punch into and out of the workpiece at a high rate of speed during a nibbling operation, means for positioning the workpiece in any direction in a horizontal plane beneath the punch and relative to a vertical axis through the center of the punch, said positioning means including workpiece holding means and drive means continuously operating during a nibbling operation for moving the workpiece holding means relative to said vertical axis, and means for providing a pause in the relative movement between said workpiece holding means and said vertical axis while the punch is engaged in the workpiece and for restoring the relative position between the workpiece holding means and the vertical axis to the relative position each would have had if there had been no pause in relative movement for allowing the punch reciprocating means and the drive means to be operated continuously as the workpiece is moved in any direction in said horizontal plane while being punched without permanently affecting the relative position between the workpiece holding means and the vertical axis during an entire nibbling operation.
 13. Nibbling apparatus for rapidly punching an opening in an independent workpiece sheet comprising means for reciprocating a punch into and out of a sheet at a high rate of speed, means for positioning the sheet beneath the punch in the X and Y axes, said positioning means including sheet holding means and drive means for moving the sheet holding means in the X and Y axes, and sheet floating means for allowing the punch reciprocating means and the drive means to be operated continuously without bending the sheet as the sheet is being punched, said sheet floating means including means operable to move the sheet with the drive means while the punch is disengaged from the sheet, to allow the punch to stop the sheet when the punch is in the sheet by effecting relative movement between the holding means and the drive means, and to reposition the holding means relative to the drive means when the punch is removed from the sheet to return the sheet to a position which it would have had if not stopped by the punch. 